Please complete the following questions. It is important that you show all work you did to solve the problems when you submit your work. This includes any calculations, diagrams, or graphs that helped you solve it.
7-6
Rational Exponents
Main Ideas
• Write expressions
with rational
exponents in radical
form and vice versa.
• Simplify expressions
in exponential or
radical form.
GET READY for the Lesson
Astronomers refer to the space
around a planet where the planet’s
gravity is stronger than the Sun’s as
the sphere of influence of the planet.
The radius r of the sphere of
influence is given by the formula
(MM)
r=D
M
where My is the mass
of the planet, M, is the mass of the
Sun, and D is the distance between the planet and the Sun.
Rational Exponents and Radicals You know that squaring a number
and taking the square root of a number are inverse operations. But how
would you evaluate an expression that contains a fractional exponent
such as the one above? You can investigate such an expression by
assuming that fractional exponents behave as integral exponents.
(69)? = b. b)
Write the square as multiplication.
= bż + Ź
Add the exponents.
= b1 or b Simplify.
1
1
Thus, bā is a number whose square equals b. So b2 = Vb.
1
bn
KEY CONCEPT
Words For any real number b and for any positive integer n, bħ= vb,
except when b< 0 and n is even.
Example 83= or 2
EXAMPLE Radical and Exponential Forms
1
a. Write a 4 in radical form. b. Write Vy in exponential form.
a) = vā Definition of bă Vy 1 = y; Definition of bi
CHECK Your Progress
1B. VC
1A. x
Lesson 7-6 Rational Exponents 415
7-7
Solving Radical Equations
and Inequalities
GET READY for the Lesson
Main Ideas
• Solve equations
containing radicals.
• Solve inequalities
containing radicals.
Computer chips are made from the element silicon, which is found in
sand. Suppose a company that manufactures computer chips uses the
formula C = 10n3 + 1500 to estimate the cost C in dollars of
producing n chips. This can be rewritten as a radical equation.
New Vocabulary
radical equation
extraneous solution
radical inequality
Solve Radical Equations Equations with radicals that have variables in
the radicands are called radical equations. To solve this type of equation,
raise each side of the equation to a power equal to the index of the
radical to eliminate the radical.
It is very important that you check your solution. Sometimes you will
obtain a number that does not satisfy the original equation. Such a
number is called an extraneous solution.
EXAMPLE
Solve Radical Equations
Solve each equation.
a. Vx+1+2 = 4
Vx + 1 + 2 = 4 Original equation
Vx + 1 = 2
(Vx+1)2 = 22 Square each side to eliminate the radical.
Subtract 2 from each side to isolate the radical.
x+1=4
Find the squares.
x= 3
Subtract 1 from each side.
CHECK V x + 1 + 2 = 4 Original equation
V3+1 +224
Replace x with 3.
4= 4 Simplify.
The solution checks. The solution is 3.
b. Vx – 15 = 3 – VX
V x – 15 = 3 – VX Original equation
(Vx – 15)2 = (3 – Væ)2 Square each side.
X – 15 = 9 – 6VX + x Find the squares.
-24 = -6vx
Isolate the radical.
Divide each side by - 6.
4=vx
42 = (Vx)?
Square each side again.
16 = x
Evaluate the squares.
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